Various kinds of square cut or square end gusseted bags have been previously proposed for popping corn in a microwave oven. U.S. Pat. No. 4,691,374 describes a cooking bag in which diagonal gusset seals are shown at the bottom of the bag (FIGS. 1, 3 and 4). Although very good, the bag does have certain shortcomings. It will be noticed that the bag in FIG. 9 has a generally oval shape resembling an inflated football. In the work leading to the present invention, we have now discovered that the tendency of the bag to form an oval or football shape during popping in the oven has a bearing on the effectiveness of the susceptor (microwave interactive sheet material) provided in one face of the bag for absorbing microwave energy and transferring the energy in the form of heat to pop the corn. It was also discovered that where the lower panel of the bag begins to bend upwardly at each end the bag tended to scorch, primarily because the food was not in contact with the susceptor at that point.
In view of these shortcomings, it is an important objective of the invention to find a way to improve the shape of the package as it expands during popping of corn in a microwave oven to allow the susceptor provided in one face panel of the bag to operate more effectively. It is another object to find a way of changing the shape of the bag so that the susceptor can be made larger in size without causing excessive scorching, charring or burning. Another object is to find a way during expansion of the bag in a microwave oven to maintain one face, particularly the lower face of the bag, in a flat condition so that it conforms better to the floor of the microwave oven. Another object is to increase the area of the lower face panel. A more general object is to find a way of controlling the shape of a microwave corn popping bag to improve the performance of the bag as measured by the volume of popped corn, the expansion density of the popped corn, the number of unpopped kernels, steam venting reliability and bag scorching.
These and other more detailed and specific objects of the present invention will be apparent in view of the following description setting forth by way of example but a few of the various forms of the invention that will be apparent to those skilled in the art once the principles described herein are understood.